!*************************************************************************
!*           EVALUATE A COMPLEX POLYNOMIAL BY HORNER'S METHOD            *
!* --------------------------------------------------------------------- *
!* SAMPLE RUN:                                                           *
!*                                                                       *
!*   EVALUATE A CPMPLEX POLYNOMIAL BY HORNER'S METHOD                    *
!*                                                                       *
!*  Example: P(Z) = (1+i) Z^4 + (2-i) Z^3 +(3+0.5i) Z^2 + (4-2i) Z       *
!*                + (5-0.75i)                                            *
!*                                                                       *
!*  For Z = (1.500000,2.000000)                                          *
!*                                                                       *
!*  P(Z)  = (-28.93750,-6.937500)                                        *
!*                                                                       *
!*                                                                       *
!*                                F90 Release 1.0 By J-P Moreau, Paris   *
!*                                         (www.jpmoreau.fr)             *
!*************************************************************************  
PROGRAM TEST_CHORNER     !uses intrinsic complex

integer, parameter :: NMAX = 25


  COMPLEX A(0:NMAX), Z, Y0
  integer N

  N = 4      ! ORDER OF POLYNOMIAL

! define complex coefficients
  A(4) = cmplx(1.0, 1.0)       ! power 4
  A(3) = cmplx(2.0,-1.0)       ! power 3
  A(2) = cmplx(3.0, 0.5)       ! power 2
  A(1) = cmplx(4.0,-2.0)       ! power 1
  A(0) = cmplx(5.0,-0.75)      ! power 0

  Z= cmplx(1.5, 2.0)   ! complex argument

  print *,' '
  print *,'  EVALUATE A COMPLEX POLYNOMIAL BY HORNER''S METHOD'
  print *,' '

  call CHorner(A, N, Z, Y0)

  write(*,10,advance='no'); write(*,*) Z
  print *,' '
  write(*,11,advance='no'); write(*,*) Y0
  print *,' '

10 format('  For Z = ')
11 format('  P(Z)  = ')

  stop

END

 
  Subroutine CHorner(A, N, X0, Y)
  integer, parameter :: NMAX = 25
    COMPLEX A(0:NMAX), X0, Y
    Y = A(N)
	do i=N-1,0,-1
      Y = Y*X0 + A(i)
    end do
	return
  end

! end of file chorner.f90